1 Barracuda 18LP Disc Drive ST39175LW/LC ST318275LW/LC Installation Guide
2 Contents Preface...1 Electrostatic discharge protection...1 Important safety information and precautions...2 Wichtige Sicherheitshinweise... 4 Regulatory agency compliance...7 Seagate Technology support services...9 General description...15 Initial setup information Kühlung des Systems...30 Installation des Laufwerkes und Anschluß der Kabel...32 LW drives section...40 LC drives section Seagate Technology, Inc. All rights reserved Publication Number: , Rev. B May 1999 Seagate, Seagate Technology, and the Seagate logo are registered trademarks of Seagate Technology, Inc. Barracuda, SeaFAX, SeaFONE, SeaBOARD, and SeaTDD are either trademarks or registered trademarks of Seagate Technology, Inc. or one of its subsidiaries. All other trademarks or registered trademarks are the property of their respective owners. No part of this publication may be reproduced in any form without written permission from Seagate Technology, Inc.
3 Barracuda 18LP Installation Guide, Rev. B 1 Preface This manual contains information for users of the Seagate Barracuda 18LP SCSI disc drives. It provides support services, performance specifications, and initial setup information. Additional information is available in the Barracuda 18LP Product Manual (part number ). Contact your Seagate sales representative if you need to order this publication. Note. If any differences exist between specification values in this guide and the product manual, the product manual values are the authoritative values. Electrostatic discharge protection Caution. Removal of circuit boards by personnel not performing depot repair will damage components and may void the warranty. All drive electronic assemblies are sensitive to static electricity, due to the electrostatically sensitive devices used within the drive circuitry. Although some devices such as metal-oxide semiconductors are extremely sensitive, all semiconductors, as well as some resistors and capacitors, may be damaged or degraded by exposure to static electricity. Electrostatic damage to electronic devices may be caused by the direct discharge of a charged conductor or by exposure to the static fields surrounding charged objects. To avoid damaging drive electronic assemblies, observe the following precautions when installing or servicing the drive: Ground yourself to the drive whenever the drive electronics are or will be exposed. Connect yourself to ground with a wrist strap (Seagate part number ). Connection may be made to any grounded metal assembly. As a general rule,
4 2 Barracuda 18LP Installation Guide, Rev. B remember that you and the drive electronics must all be grounded to avoid potentially damaging static discharges. Turn off the power before removing or installing the DC power cable. Do not remove any circuit boards from the drive. Never use an ohmmeter on any circuit boards. When installing the drive on a carrier or tray, discharge the carrier or tray prior to inserting it into the system. Important safety information and precautions Caution. Use forced-air ventilation when bench-testing the drive to ensure proper cooling of drive components. Use proper safety techniques for safe, reliable operation of this unit. The procedures in this manual and labels on the unit contain warnings and cautions that must be carefully read and followed to minimize or eliminate the risk of personal injury. The warnings point out conditions or practices that may endanger you or others. The cautions point out conditions or practices that may damage the unit, possibly making it unsafe for use. Always observe the following warnings and precautions: Follow all cautions and warnings in the procedures. Use sound safety practices when operating, installing, or removing the unit. Use caution when troubleshooting a unit that has voltages present. Turn off power to the unit before removing it. Ensure that the internal temperature of the rack or cabinet does not exceed the limits defined for the drive when the drive is mounted in an equipment rack or cabinet. When units are
5 Barracuda 18LP Installation Guide, Rev. B 3 stacked vertically, pay special attention to the top where temperatures are usually highest. Follow the precautions listed above in Electrostatic discharge protection. Do not remove any circuit boards from the drive. Return the entire drive for depot repair if any circuit board is defective. Removal of circuit boards by personnel not performing depot repair will damage components and may void the warranty. Do not remove the head and disc assembly (HDA) from the drive. Return the entire drive for depot repair if the HDA is defective. Do not attempt to disassemble the HDA. It is not field repairable. If the sealed HDA is opened by personnel not performing depot repair, this will damage components and void the warranty. As a component, this drive is designed to be installed and operated in accordance with UL1950, EN60950, CAN/CSA C , and VDE0805. Seagate takes all reasonable steps to ensure that its products are certifiable to currently accepted standards. Typical applications of these disc drives include customer packaging and subsystem design. Safety agencies conditionally certify component assemblies, such as the Barracuda disc drive, based on their final acceptability in the end-use product. The subsystem designers are responsible for meeting these conditions of acceptability in obtaining safety-regulatory agency compliance in their end-use products and for certifying where required by law. A necessary part of meeting safety requirements is the provision for overcurrent protection on drive SELV supply voltages.
6 4 Barracuda 18LP Installation Guide, Rev. B This unit is a component part and as such is not meant to comply with FCC or similar national requirements as a stand-alone unit. Engineering radiated emissions test results are available through the Seagate Safety Department to assist the subsystem designer. Wichtige Sicherheitshinweise Vorsicht. Beim Testen des Laufwerks auf dem Prüftisch ist Fremdbelüftung vorzusehen, um eine ausreichende Kühlung der Laufwerkkomponenten sicherzustellen. Verwenden Sie geeignete Sicherheits- um den sicheren, zuverlässigen Betrieb dieser Einheit zu gewährleisten. Die Verfahren in diesem Handbuch und die Aufkleber auf dem Gerät enthalten Warn- und Vorsichtshinweise. Diese Hinweise sind sorgfältig durchzulesen und zu beachten, um das Risiko von Verletzungen auf ein Mindestmaß zu beschränken oder ganz zu vermeiden. Die Warnhinweise machen auf Situationen oder Praktiken aufmerksam, die Sie oder andere gefährden könnten. Die Vorsichtshinweise machen auf Situationen oder Praktiken aufmerksam, die Einheit beschädigen können, so daß deren Gebrauch mit Risiko behaftet ist. Die Warn- und Vorsichtshinweise sind nicht allumfassend! Es ist uns einfach nicht möglich, alle Wartungsmethoden oder die eventuellen Risiken jeder Methode zu kennen, zu beurteilen und Sie entsprechend zu beraten. Aus diesem Grund haben wir auf eine derartige umfassende Beurteilung verzichtet. Falls Sie ein hier nicht beschriebenes Verfahren oder Werkzeug verwenden, stellen Sie zuerst sicher, daß das gewählte Verfahren weder Ihre persönliche Sicherheit noch die Leistung der Einheit gefährdet.
7 Barracuda 18LP Installation Guide, Rev. B 5 Beachten Sie in jedem Fall die folgenden Warn-und Vorsichtshinweise: Beachten Sie alle Warn- und Vorsichtshinweise in diesem Handbuch. Treffen Sie beim Betrieb, bei der Installation oder bei der Entfernung der Einheit angemessene Sicherheitsvorkehrungen. Wenn eine Einheit unter Spannung steht, gehen Sie bei der Fehlerdiagnose besonders vorsichtig vor. Schalten Sie die Einheit aus, bevor Sie mit den Installations-und Entfernungsarbeiten beginnen. Wenn das Laufwerk in einem Einbaugestell oder Gehäuse montiert ist, sorgen Sie dafür, daß die Temperatur im Inneren des Gestells oder Gehäuses die für das Laufwerk vorgegebenen Grenzwerte nicht übersteigt. Wenn Einheiten vertikal übereinander betestigt werden, achten Sie besonders auf den oberen Stapelbereich, da dort die Temperatur gewöhnlich am höchsten ist. Befolgen Sie die oben unter Electrostatic Discharge Protection angegebenen Sicherheitsmaßnahmen. Nehmen Sie keine Platinen aus dem Laufwerk. Wenn eine Platine defekt ist, muß das gesamte Laufwerk zur Reparatur eingeschickt werden. Die Herausnahme von Platinen durch andere Personen als die für die werkseitige Reparatur zuständigen kann zu einer Beschädigung der Komponenten und Erlöschen des Garantieanspruchs führen. Die vormontierte Kopf- und Festplatteneinheit (HDA) nicht aus dem Laufwerk nehmen! Falls die HDA beschädigt ist, schicken Sie das gesamte Laufwerk zur Reparatur ein.
8 6 Barracuda 18LP Installation Guide, Rev. B Die HDA ist nicht vor Ort reparierbar und darf nicht auseinandergenommen werden! Öffnen der versiegelten HDA durch andere Personen als die für die werkseitige Reparatur zuständigen hat eine Beschädigung der Komponenten und Erlöschen des Garantieanspruchs zur Folge. Als Teilkomponente ist dieses Laufwerk für die Installation und den Betrieb in Übereinstimmung mit UL 1950, EN60950, CAN/ CSA C und VDE0805 vorgesehen. Seagate ist ständig bemüht, die Zulassungsfähigkeit von Seagate-Produkten im Rahmen der gegenwärtig geltenden Standards zu gewährleisten. Zu den typischen Anwendungen dieser Festplattenwerke zählen Systemeinbau durch den Kunden und die Konstruktion von Untersystemen. Sicherheitsbehörden gewähren eine bedingte Zulassung für Komponenten wie das Barracuda-Festplattenlaufwerk vorbehaltlich der endgültigen Zulasssung im Endprodukt. Designer von Untersystemen sind dafür verantwortlich, die Voraussetzungen für die Einhaltung sicherheits- oder aufsichtsbehördlicher Vorschriften in ihren Endprodukten und - falls gesetzlich vorgeschrieben - für die Zulassung zu schaffen. Eine Grundvoraussetzung zur Einhaltung der Sicherheitsanforderungen ist die Bereitstellung eines Überlastschutzes für die SELV-Versorgungsspannungen des Laufwerks. Dieses Gerät ist eine Baugruppe und unterliegt als solche nicht den Anforderungen der FCC oder ähnlicher nationaler Behörden für eigenständige Geräte. Technische Testergebnisse zu elektromagnetische Strahlung sind für Designer von Untersystemen auf Anfrage von der Seagate-Sicherheitsabteilung erhältlich.
9 Barracuda 18LP Installation Guide, Rev. B 7 Regulatory agency compliance Electromagnetic susceptibility As a component assembly, the drive is not required to meet any susceptibility performance requirements. It is the responsibility of those integrating the drive within their systems to perform those tests required and design their system to ensure that equipment operating in the same system as the drive or external to the system does not adversely affect the performance of the drive. See Table 2, DC power requirements. Electromagnetic compliance Seagate uses an independent laboratory to confirm compliance to the directives/standard(s) for CE Marking and C-Tick Marking. The drive was tested in a representative system for typical applications. The selected system represents the most popular characteristics for test platforms. The system configurations include: 486, Pentium, and PowerPC microprocessors 3.5-inch floppy disc drive Keyboard Monitor/display Printer External modem Mouse Although the test system with this Seagate model complies to the directives/standard(s), we cannot guarantee that all systems will comply. The computer manufacturer or system integrator shall confirm EMC compliance and provide CE Marking and C- Tick Marking for their product.
10 8 Barracuda 18LP Installation Guide, Rev. B Electromagnetic compliance for the European Union If this model has the CE Marking it complies with the European Union requirements of the Electromagnetic Compatibility Directive 89/336/EEC of 03 May 1989 as amended by Directive 92/31/ EEC of 28 April 1992 and Directive 93/68/EEC of 22 July Australian C-Tick If this model has the C-Tick Marking it complies with the Australia/New Zealand Standard AS/NZS and meets the Electromagnetic Compatibility (EMC) Framework requirements of Australia s Spectrum Management Agency (SMA).
11 Barracuda 18LP Installation Guide, Rev. B 9 Seagate Technology support services Online Services Internet For online information about Seagate products, visit or your disc or tape questions to: Presales Support: Disc: _presales.shtml or Tape: _tape_presales.shtml or Technical Support: Disc: _disc_support.shtml or Tape: _tape_support.shtml or SeaBOARD is a computer bulletin board system that contains information about Seagate disc and tape drive products and is available 24 hours daily. Set your communications software to eight data bits, no parity and one stop bit (8-N-1). This service is available worldwide. Automated Services SeaFONE (1-800-SEAGATE) is Seagate's toll-free number ( ) to access our automated self-help services. Using a touch-tone phone, you can find answers to service phone numbers, commonly asked questions, troubleshooting
12 10 Barracuda 18LP Installation Guide, Rev. B tips and specifications for disc drives and tape drives 24 hours daily. International callers can reach this service by dialing SeaFAX is Seagate's automated FAX delivery system. Using a touch-tone phone, you can obtain technical support information by return FAX 24 hours daily. This service is available worldwide. Presales Support Our Presales Support staff can help you determine which Seagate products are best suited for your specific application or computer system. Seagate Express You can purchase select tape products and tape accessories through Seagate Express 24 hours daily by calling or by faxing your order to: Technical Support If you need help installing your drive, consult your dealer. Dealers are familiar with their unique system configurations and can help you with system conflicts and other technical issues. If you need additional help, you can talk to a Seagate technical support specialist. Before calling, note your system configuration and drive model number (ST####). SeaTDD ( ) is a telecommunications device for the deaf (TDD). You can send questions or comments 24 hours daily and exchange messages with a technical support specialist from 8:00 A.M. to 12:15 P.M. and 1:30 P.M. to 6:00 P.M. (central time) Monday through Friday.
13 Barracuda 18LP Installation Guide, Rev. B 11 Customer Service (CSO) Warranty Repair Seagate offers worldwide customer support for Seagate drives. Seagate direct OEM, Distribution and System Integrator customers should contact their Seagate service center representative for warranty information. Other customers should contact their place of purchase. Authorized Service Centers If you live outside the US, you can contact an Authorized Service Center for service or repair. USA/Canada/Latin America Support Services Presales Support Disc: or FAX: Tape: or FAX: Technical Support (SeaFONE) SEAGATE or (for specific product phone number) FAX: Disc: ; Tape: SeaFAX SEAGATE SeaTDD SeaBOARD Disc: ; Tape:
14 12 Barracuda 18LP Installation Guide, Rev. B Warranty Repair USA FAX: Mexico and Latin America FAX: Authorized Service Centers Brazil MA Informatica FAX: Canada Memofix FAX: Adtech or FAX: European Support Services For European customer support, dial the toll-free number for your specific country for presales support, technical support, SeaFAX and warranty repair. If your country is not listed here, dial our European call center at from 8:30 A.M. to 5:00 P.M. (European central time) Monday through Friday. The European call center is located in Amsterdam, The Netherlands. Call Center Austria Belgium Denmark France Germany Ireland Authorized Service Centers
15 Barracuda 18LP Installation Guide, Rev. B 13 Italy Netherlands Norway Poland Spain Sweden Switzerland Turkey United Kingdom SeaBOARD Germany Fax Services All European Countries Presales/Technical Support/Warranty Repair Africa/Middle East Support Services For presales, technical support, warranty repair and FAX services in Africa and the Middle East, dial our European call center at from 8:30 a.m. to 5:00 p.m. (European central time) Monday through Friday, or send a FAX to The European call center is located in Amsterdam, The Netherlands. Asia/Pacific East Support Services Technical Support Australia FAX: Hong Kong FAX: Japan FAX: Singapore FAX: Taiwan FAX:
16 14 Barracuda 18LP Installation Guide, Rev. B SeaFAX Australia Warranty Repair Japan FAX: Asia/Pacific and FAX: Australia
17 Barracuda 18LP Installation Guide, Rev. B 15 General description Barracuda 18LP SCSI disc drives are high-speed, randomaccess digital-data storage devices. The drive is a component for installation in an enclosure designed for the drive. This is often a rack within the system or an external enclosure designed to house one or more disc drives or other peripheral units. In either case, the disc drive must receive adequate cooling (refer to Providing adequate cooling ) and it must be sufficiently grounded and shielded from emissions. The Barracuda 18LP Product Manual (part number ) contains guidelines for a properly designed enclosure. * *Model LW version with 68-pin SCSI I/O connector Figure 1. Barracuda 18LP family drive
18 16 Barracuda 18LP Installation Guide, Rev. B Table 1. Drive characteristics Interface UltraSCSI  Capacity Formatted  Max. data blocks  ST Gbyte  10F59C7h  ST Gbyte  21EB38Fh  Recording Cylinders (user) 11,721 Read/write data heads ST ST Access time  Average read 6.9 msec Average write 7.7 msec Disk rotation RPM 7,200 r/min Average latency 4.17 msec Internal transfer rate (variable with zone) ST Mbits/sec ST Mbits/sec Maximum synchronous SCSI transfer rate LW/LC 80 Mbytes/sec  Operated according to SCSI-2 and SCSI-3 protocols. Referred to also as SCSI Fast-20 and Fast-40.  Read data capacity. Add one for total capacity. Standard factory units are formatted 512 data bytes per sector with spare tracks reserved for reallocating bad sectors.  Includes controller overhead.
19 Barracuda 18LP Installation Guide, Rev. B 17 Table 2. DC power requirements (Amps), multimode (SE/LVD) ST39175LW/LC ST318275LW/LC Voltage +5V +12V +5V +12V Regulation  ±5% ±5% ±5% ±5% Avg. idle current DCX  Max. starting current (peak DC)  (peak AC)  Delayed motor start (max)  Peak operating current Typical DCX  Maximum DC  Maximum (peak)  Measured with an average reading DC ammeter. Instantaneous +12V current peaks will exceed these values.  A 10% droop is permissible during initial start of the spindle but must return to ±5% before reaching 7,200 RPM. The ±5% must be maintained after the drive signifies that its power-up sequence has been completed and that the drive is able to accept selection by the host initiator.  See the +12V current profile in the Barracuda 18LP Product Manual (publication number ).  This condition occurs when the Motor Start option is enabled and the drive has not yet received a Start Motor command.
20 18 Barracuda 18LP Installation Guide, Rev. B  See Conducted noise immunity in the Barracuda 18LP Product Manual. The specified voltage tolerance is inclusive of ripple, noise, and transient response.  Operating condition is defined as random seek read operations with a block count of 64. General Notes from Table Minimum current loading for each supply voltage is not less than 4% of the maximum operating current shown. 2. Use separate ground returns for +5V and +12V supplies. 3. Where power is provided to multiple drives from a common supply, carefully consider individual drive power requirements. Where multiple units are powered on simultaneously, be sure the peak starting current is available to each device. Table 3 shows the nominal (no tolerance specified) dimensions and weight of the drive. Table 3. Dimensions of the drive inches mm Height Width Depth Weight 1.5 pounds (0.589 kilograms)
21 Barracuda 18LP Installation Guide, Rev. B 19 Initial setup information The general information beginning on this page applies to all of the Barracuda 18LP drive models. After reading the general information topics, refer to the appropriate drive-specific section listed below for additional information about configuring and installing your particular model. Drive models Page ST39175LW ST318275LW 40 ST39175LC ST318275LC 45 General information The following general information topics are discussed: SCSI ID jumpers Drive termination Terminator power Interface drivers and data path width notes Other applicable jumper options Providing adequate cooling Mounting the drive and connecting cables 1 Formatting the drive 1 This mounting procedure does not apply to LC model drives. To mount an LC drive, plug the drive into the system s single connector attachment (SCA) position on the system s back panel.
22 20 Barracuda 18LP Installation Guide, Rev. B SCSI ID jumpers Each device on the SCSI chain must have a unique SCSI ID. The host system s SCSI controller usually uses the ID that has the highest priority interrupt in the SCSI I/O system. This is always ID7. ID0 is lowest priority in an 8-bit I/O system. ID8 is lowest priority in a 16-bit I/O system. The lower priority SCSI IDs are normally used for other SCSI devices such as this Barracuda disc drive. Note. Most SCSI controllers (host adapters) allow you to skip a SCSI ID. For example, you can have ID0, ID1, and ID3 (skipping ID2). Other controllers do not allow this so be sure to refer to your system or controller user s manual for details about its requirements for proper SCSI device installation. Note. This drive is a SCAM (SCSI Configured Auto Magically) compliant drive. If the system into which you are installing this drive requires SCAM compliant drives, you do not need to be concerned about the drive ID jumper settings, as the system automatically assigns your new drive the ID it wants it to have. The system may or may not use the existing drive ID jumper settings. Setting the drive ID doesn t hurt anything, but is not necessary in a SCAM compliant system. Most Barracuda disc drives are factory set with the SCSI ID set at 0. To change the SCSI ID, refer to the appropriate drive section for your model. If, after completing the installation process, the drive s LED does not show on/off activity when the host is trying to communicate with the drive, a duplicate SCSI ID may be the problem. If this is
23 Barracuda 18LP Installation Guide, Rev. B 21 the case, change the ID so that each device on the SCSI chain has its own unique ID. Also check your system or controller user s manual to ensure that you have not violated its SCSI ID numbering recommendations. Drive termination If you are installing a Barracuda drive in a system that has other SCSI devices installed, terminate only the end devices on the SCSI chain. A SCSI device is any disc drive, scanner, tape backup unit, or other piece of hardware connected to your system using the SCSI bus. The top example in Figure 2 shows an internal hard disc at one end of the SCSI bus with the SCSI controller at the other end (both are terminated). The bottom example shows two additional SCSI devices connected externally this means the SCSI controller is no longer on the end of the SCSI chain and should not be terminated. Note. Some controllers prefer to remain terminated even if they are in the middle of the chain. Also, some controllers treat the internal and external chains as separate logical buses. This means you may need to terminate both the first and last devices on both logical buses to achieve proper termination. If necessary, refer to your system or controller documentation to see how this is handled in your particular system.
24 22 Barracuda 18LP Installation Guide, Rev. B For information about how to terminate your drive, refer to the appropriate drive-specific section. Internal SCSI cable Internal SCSI device Internal SCSI device Controller Internal SCSI device Terminate Internal SCSI cable Internal SCSI device Controller External SCSI cable External SCSI device External SCSI device Figure 2. Terminate SCSI bus termination Terminator power You usually will not need to change this option and can normally leave the drive configured as it was shipped from the factory. For information about how to change the terminator power option on your drive, refer to the appropriate drive-specific section. I/O circuits and data path widths Note. Make sure your system I/O controller circuit board has the proper I/O circuits to communicate with this drive. You may have to replace your old controller with a newer one having the proper I/O circuits. The following paragraphs and tables will help you to know whether you want to operate the drive I/O circuits in single-ended (SE) mode or low voltage differential (LVD) mode. If your old I/O controller operated the I/O circuits in differential mode, chances are it was high voltage differential mode (HVD).
25 Barracuda 18LP Installation Guide, Rev. B 23 This drive must not be operated with that kind of controller. This drive can operate with older SE controllers, however. LW and LC models use SCSI multimode I/O circuits. Multimode circuits operate either in single-ended mode or low voltage differential mode. No high voltage differential devices should be connected in the I/O daisy chain with LW or LC model drives. The state of the I/O DIFFSNS line determines whether the devices on the SCSI bus operate their I/O circuits in single-ended or low voltage differential mode. The host device on the SCSI bus operates the DIFFSNS line. However, the SE jumper on J2 forces DIFFSNS to nominal ground (see Figure 12). The host device cannot override the SE jumper. If DIFFSNS is at nominal ground (0V to.6v), all of the bus receivers/drivers operate in single-ended mode. If DIFFSNS is between.7v and 1.9V, all bus receiver/drivers operate in low voltage differential (LVD) mode. LC and LW models have a wide (16-bit) SCSI data bus rather than the standard (non-wide) 8-bit SCSI data bus; however, you can use these wide drives on a standard (non-wide) 8-bit data bus. However, the unused lines must be terminated the same as the used lines. Figures 3a, 3b, and 3c show typical drive connections. The following tables list the maximum cable lengths and number of devices allowed on a daisy-chain cable for I/O data transfer rates shown. Note. For LVD operation, twisted pair cables are recommended. For LVD Fast-40 operation, twisted pair cables are strongly recommended. For Fast-80 operation, twisted pair cables are required.
26 24 Barracuda 18LP Installation Guide, Rev. B Table 4a. Cable characteristics for single-ended I/O circuits Number of attached SCSI devices Maximum distance between terminators (meters)   Fast-5 Fast-10 Fast-20 Fast-40 1 to 4 maximum capacitance (25 pf) SCSI devices N/A 5 to 8 maximum capacitance (25 pf) SCSI devices N/A 9 to 16 maximum capacitance (25 pf) SCSI devices 6 3  N/A  For environments where all elements of the bus (cables, device interfaces, environmental noise and other parameters) are controlled to be better than minimally required, it may be possible to extend the path length and device count.  Extending the device count beyond eight requires specification control beyond the minimum specified in the ANSI T10/1142D document. It is recommended that the devices be uniformly spaced between terminators with the end devices located as close as possible to the terminators.  Values specified by data rate shall apply even if a slower data rate is negotiated.
27 Barracuda 18LP Installation Guide, Rev. B 25 Table 4b. Interconnect Cable characteristics for differential I/O circuits Maximum distance between terminators (meters)   Fast-5 Fast-10 Fast-20 Fast-40 Point-to-point interconnect (2 devices)  Daisy-chain interconnect (up to 16 devices)   For environments where all elements of the bus (cables, device interfaces, environmental noise and other parameters) are controlled to be better than minimally required, it may be possible to extend the path length and device count.  SCSI devices shall be within a stub length of the termination (.1 meter).  Values specified by data rate shall apply even if a slower data rate is negotiated.  Loads spaced at least 8 inches (20.3 cm) apart (refer to SCSI EPI T10/1143D specification).
28 26 Barracuda 18LP Installation Guide, Rev. B Power Cable Figure 3a. Sixty-eight pin connection to LW model drive